The long-term goal of this project is to develop a minimally invasive treatment for cancers in the upper abdomen, including primary and metastatic tumors in the liver, and renal cell carcinoma. Specific aims of the project are to 1) design, fabricate, and evaluate handheld phased array focused ultrasound therapy probes for treating liver and renal tumors under MR guidance, 2) develop MRI imaging software to accurately map the tissue temperature in the upper abdomen, and 3) perform initial testing and evaluation of the system. Focused ultrasound is a promising technique for the next generation of non-invasive cancer therapy systems. With this technology, ultrasound energy is focused at a point deep within the body to thermally ablate targeted tissue. This can be done with minimal heat deposition at the skin surface and without skin puncture or incision. The effort proposed here addresses the main technical challenges to using focused ultrasound therapy in the upper abdomen. Techniques and systems will be developed to couple focused ultrasound treatment with Magnetic Resonance image guidance to allow precise targeting of the thermal energy to target tissues. Techniques to monitor heat deposition through accurate temperature mapping will be developed to insure that the entire target volume is being treated, and to determine if critical structures such as vessels, the gall bladder and the diaphragm remain sufficiently cool to avoid damage. Since organs in the upper abdomen move during breathing, MRI thermal imaging sequences that compensate for motion will be developed. The new techniques and systems will be developed on phantoms and tested in porcine animal models. Relevance: Colorectal cancer is the third leading cause of cancer related deaths in men and women. Many of these deaths are associated with colorectal metastases to the liver. Similarly, renal cell carcinoma is an often fatal malignancy which is increasing in incidence in the US. Minimally invasive thermal therapies are showing promising results in the treatment of these conditions, but many technical challenges remain. The work proposed here addresses these challenges and if successful, will represent a major advance in the non-invasive treatment of cancer.